Selected trace fossils from the type section of the ' Etcheminian Series' at Hanford Brook are described and illustrated: Helmithoidichnites lenuis Fitch, Monocraterion sp., Palaeophycus tubular is Hall, Planolites sp., Psammichnites gigas Matthew, Subphyllochordral sp., Taphrhelminthoida dailyi n. sp., and Taphrhelminthopsis cf. T. circularis Crimes et al. The assemblage has elements comparable to those in other Lower Cambrian sequences. It formed in shallow water settings, is mainly endichnial, and contains systematic, guided meander traces that are generally characteristic of deep-water environments in younger sequences; this may be related to global environmental changes early in the Palaeozoic. The guided meander traces are characterized morphometrically, using an image analyser: the meander systems exhibit a strongly bimodal distribution of morphologic elements, reflecting a well developed taxis (sense for position, direction, and distance) during trace production. The method of morphometric analysis has potential for characterizing trace fossils generally, somewhat like X-ray diffractograms characterize minerals.
Canada 3 E3L 4L5Flute, load and groove cases occur widely at the sharp Interfaces of slltstone diapirs, injection lenses, and pods In fluvial sandstone of the Boss Point Formation of southeastern New Brunswick.These concordant and discordant injection features range from approximately 20 centimetres (pods) to many metres (injection lenses) in diameter. They are confined to "brecciform intervals" that can be traced along strike and dip for a hundred metres or more.The flute, load and groove casts on the injection surfaces, have evidently not been formed by any primary sedimentary process but are the result of liquefaction, 9ediment injection and flow moulding during postdepositional compaction of the strata. The term "rheoplasis" la proposed to denote this process, and the general term "rheoplastic structures" or "rheoplasts" refers to the range of sole-marking like structures formed as a result of this process.The realization that flute casts can form as a result of post-deposltional processes is of great significance In the classification of sedimentary structures and the' interpretation of deposltional environments and attendant sedimentary processes.Au sud-est du Nouveau-Brunswick, dans les grSs fluviatiles de la formation de Boss Point, on peut voir de nombreux exemples de flutes, empreintes de charge et cannelures aux interfaces distincts de diapirs de siltstone, de lentilles d'injection, de mottes et de loupes. Ces elements d'injection sont concordants ou discordants et possedent un diametre allant de 20 cm (pour les loupes) Jusqu'S plusieurs metres (pour les lentilles d'injection). lis sont egalemenr. restreints 3 des "intervalles brechiques" que l'on peut suivre sur des centaines de metres et plus, le long de la direction et du pendage de la stratification.Les flutes, cannelures et empreintes de charge que l'on retrouve sur les surfaces d'injection ne resultent evidemroent pas d'un processus sedimentaire primaire mais plutot de la liquefaction, de 1'injection du sediment et du moulage des coulees durant la compaction apres la deposition de la strate. Pour marquer ce procede, on propose le terme "rheoplasie" alors que le terme plus global "structures rheoplastiques" (ou "rheoplastes") s'applique aux empreintes de toutes sortes qui resultent de ce meme procede et que l'on retrouve sur la surface inferieure d'une strate.La classification des structures sedimentaires ainsi que 1'interpretation des environnements de deposition et des procedes sedimentaires connexes seront grandement influencees par le fait que des flutes peuvent resulter d'un procede post-depositionnel.[Traduit par le journal]
Injection of semi-fluid silt/water suspensions into semi-fluid sand/cement slurries resulted In the formation of a variety of structures at the Interface between the two materials. These structures resemble flute, load, groove and ridga-casts and form as a result of flow-moulding ('rheoplasis'). These experimental results complement earlier work' on certain natural occurrences of these structures and substantiate the hypothesis that they form as a result of post-depositional sediment movement and not through primary sedimentary processes. RÉSUMÉ L'injection de suspensions aqueuses sermi-fluides de limon dans des mélanges semi-fluides de sable et de ciment à produit une variete de formes à la surface de contact des deux matérlaux. Ces formes, qui resseablent aux empreintes de charge, flùtes, cannelures et crêtes, résultent du moulage d'une coulée ('rheoplasle'). Les resultats de ces expériences complementent des travaux anterieurs qui traitent d'exemples naturels de ces formes et appulent l'hypothèse selon laquelle ces formes résultent du mouvement des sédiments après leur déposition et non pas de processus sédimentaires primaires. [Traduit par le journal]
An ornamented, dome‐shaped cavity, partially filled with mudstone, 4 m in diameter at its circular base and 1 m in height occurs in fluvial sandstone of the Carboniferous Boss Point Formation near Sackville, New Brunswick, Canada. The cavity formed by differential weathering and erosion of the mudstone. Its origin is enigmatic though its size, shape and relationship to the underlying mudstone bed on which it rests suggest a diapiric origin for the mudstone that filled it. On the other hand, the ornamentation on the cavity surface includes flute moulds, suggesting an erosional origin for the domal structure. Of the four principal hypotheses for its origin the one preferred by the authors involves formation by diapiric intrusion of semi‐fluid mud into liquefied sand, soon after deposition. The ornamentation on the cavity surface would have formed as part of the intrusion process. Structures akin to flute moulds have been produced experimentally in support of this interpretation by differential flow across a cement‐mix‐mud interface in a flow box and also by diapiric intrusion of mud in a soft cement mix. By analogy the flute moulds on the cavity surface could have been formed in the same way. By this interpretation, primary sedimentary processes need not be invoked to explain their occurrence on either this cavity surface or on the numerous other mudstone cavity surfaces that are ubiquitous in the Permo‐Carboniferous of eastern Canada. Results of this study have important implications with respect to the potential diversity of origins of flute moulds in general.
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